Recently, a fuel cell capable of achieving high output performance with a smaller quantity of catalyst has been sought from the viewpoint of reduction in manufacturing costs for fuel cells. A fuel cell having a catalyst component covered around its periphery with two different types of ionomers has been proposed as one solution for this problem. Such a fuel cell has an increased area of contact of the catalyst component with the ionomers thereby to permit effective utilization of catalysts present within pores in an electrically conductive substrate. As a result, it is recognized that this enables the performance of the catalyst to be fully utilized to thus achieve high output performance.
A fuel cell as described above has been proposed for example in Patent Literature 1, as given below. Specifically, Japanese Patent Application Publication No. 2004-281305 proposes a fuel cell having an electrode catalyst in which a first hydrogen ion conductive polymer electrolyte whose unit element piece has a small size is arranged in the vicinity of conductive carbon particles, and a second hydrogen ion conductive polymer electrolyte whose unit element piece has a large size is arranged on the outside of the first hydrogen ion conductive polymer electrolyte.